28 BOTANY. 



adhere to a greater or less extent ; sometimes this takes between an entire 

 whorl, so as to form a tube ; the stamens are then monadelpJtous. They are 

 diadelphous when forming two bundles, triaddphoiis when united into three, 

 and polyadelphous v.hen grouped into a greater number. Filaments are 

 sometimes united with the pistil to form a columna or column, as in Aselepias. 

 The column is called gynostemium, and the flowers are said to be gynan- 

 droifs. 



The Anther corresponds to the blade of the leaf, and consists of lobes with 

 cavities inclosing a fine powder called pollen, which, when mature, is dis- 

 charged by an aperture. The covering of the anther is double ; the outer is 

 called ex-otheciiim, tlie inner endothecmm. The anther usually possesses tw'o 

 lobes, corresponding to the two halves of the leaf; in each lobe there are 

 generally two cavities separated by the septum. The connective divides the 

 two lobes. An anther with four persistent cavities is called quadrilocular or 

 tetrathecal. When, as is moi-e generally the case, the septa are absorbed, the 

 anther becomes bilocular or dithecal. Sometimes there is but one cavity, con- 

 stituting the unilncidar or moiiothecal anther. The form of the anther lobes 

 varies much in different plants ; more usually they are oval or elliptical. The 

 part of the anther to which, the filament is attached is called the back, the 

 opposite being the face. The division between the lobes is marked on the 

 face of the anther by a groove or furroio, and on the face there is usually a 

 suture, along which the pollen is discharged. When the filament appears to 

 be continued along the back of the anther, this is adnate or adherent ; innate 

 or erect when it ends at the base. A versatile anther is one which is not 

 fixed immovably to the filament. Sometimes the connective is more or less 

 horizontal, and bears a lobe of the anther at each end ; it is then said to be 

 distractile. The opening of anthers to discharge the pollen is their dehis- 

 cence. This may be either longitudinal or transverse. In circnniscissile 

 dehiscence, the entire apex of the anther comes off to permit the escape of the 

 pollen. An anther is introrse when it opens on the surface next to the centre 

 of the flower, and e.rtrorse when the contrary takes place. A stamen some- 

 times degenerates and becomes sterile from the absence of a proper anther ; 

 such are called staminodia, and may present various appearances, as scales, 

 leaves, petals, (fcc. 



We have already referred to the adhesion of the filaments of the stamen 

 leaving the anthers free. These in turn may be attached without involving 

 any connexion between the filaments. In this case the flower is said to be 

 syngenesious or synantherous. Stamens whose length does not exceed that 

 of the tube of the carolla are said to be included : they are exserted when of 

 greater length. 



Although the stamens are usually of the same length, yet it often happens 

 that one or more is longer than the rest. Flowers are didynamov.s when, of 

 four stamens, two are long and two are sliort. When there are two pairs of 

 lonof stamens separated by a pair of shorter, the flower is tetradynanious. A 

 stamen is said to be declinate when it bends to one side. 



Pollen, or the powdery matter discharged from the anther, consists of 

 email independent cells which have been developed in the anther by the 

 28 



